Does Scorpion Bite Lead to

Development of Resistance to

Effect of Local Anaesthetics?

: A Case Report

Dr. MINNU MRIDUL PANDITRAO

DEPARTMENT OF ANAESTHESIOLOGY & INTENSIVE CARE

PUBLIC HOSPITAL AUTHORITY’S RAND

MEMORIAL HOSPITAL

FREEPORT, BAHAMAS

THIS CASE REPORT WAS AWRDED

“ THE BEST PAPER AWARD”IN

9TH CINGRESS OF SAAARC ASSOCIATION OF

ANAESTHESIOLOGISTS CONFERENCE, BENGALURU

26TH – 28TH August 2011

THIS CASE REPORT HAS BEEN RECENTLY PUBLISHED IN:

INDIAN JOURNAL OF ANAESTHESIA,

issue 56, volume 6, Nov-Dec 2012, page no.s 575-578.

Introduction• Failure of Local Anesthetic Block” : via various routes is a

rare but a known phenomenon !

• Various factors/causes have been considered to be

responsible for this i. e. technical difficulties, drug errors

etc.

• Even genetic factors like being a Redhead, i.e. carrying a

variants of the melanocortin-1 receptor (MC1R) gene, may

lead to resistance to not only local anaesthetics like

novocaine, lidocaine, but may make them resistant to

effects of inhalational anaesthetic agents like desflurane

• Can happen even in ‘ expert/ skillful’ hands

• May be misinterpreted as a “technical or

Skill’s failure”, causing embarrassment,

Low morale, wastage of time and resources

(needing G.A.)

• Unexplainable factors responsible for this

failure

Case Report

• 65 years old multi-para female

• Grade IV procedentia, cystocele,

rectocele and enterocele

• Posted for vaginal hysterectomy and

pelvic floor repair

Case Report ( contd.)

• Pre-op. evaluation: H/O Hypertension, controlled with

Amlodipine 2.5 mg o.d. G. P. E. Normal M. P. C. grade II Lab. Inv., X-ray, E.C.G., ECHO, were W. N.

L.

• A.S.A. Grade II. • Planned subarachnoid Block

Case Report ( contd.)

• Operative Procedure :Infusion of D.N.S. with 20 Gz. I.V. cannulaMonitoring of E.C.G., SPO2 and NIBP

Aseptic Precautions , Lumbar Puncture26 Gz. Quincke’s needle at L3-L4

interspaceSitting position3.5 ml of 0.5% hyperbaric Bupivacaine

injected after free flow of CSFPatient turned supine, with head down tilt

10o

Case Report ( contd.)

• No ‘Sensory or Motor Blockade’ observed

• Waited for 10 minutes• Increased Head down Tilt• Waited another 10 minutes• Still ‘No effect’• No changes in the vitals (PR, BP)

observed

Case Report ( contd.)

• Decision to repeat ‘Spinal Block’

• Performed by a Sr. Consultant at L2-3 Interspace

• Again 3.5 ml 0.5% Hyperbaric Bupivacaine of

different batch/ brand administered

• Patient made supine and 20o Head down tilt

• ‘ No Sensory/ Motor Block even after 30 min.

• No signs of ‘autonomic block’ seen

Case Report ( contd.)

• On specific inquiry into past history• Gave history of “Scorpion Bite” Two

times• First at 17 years on right foot• Second time, 8 months back on face,

right arm and forearm• Decided to abandon the spinal block

and to give G.A.

Case Report ( contd.)

• Standard balanced G.A.

• Injs. Glycopyrrolate, Butorphanol

• Injs. Propofol, Rocuronium

• Intubation, O2, N2O and Isoflurane, IPPV

• Surgery lasted 105 min., uneventful

• Reversed with glycopyrrolate + neostigmine, extubated

• After recovery no signs of residual/delayed spinal block

• Follow up for 48 hours, uneventful.

Case Report ( contd.)

• Patient called in the O.T. on 8th post op. day

• Condition explained

• Informed consent obtained

• Peripheral Nerve Blocks of Median, Ulnar and Anterior

interosseous br. of Radial nerve given at the level of

left wrist with 0.5% bupivacaine

• Local infiltration of the skin of the left forearm was

done with 3 ml. of 2% xylocaine with adrenaline

Case Report ( contd.)

• Confirming our suspicion, there was neither any

sensory nor motor block observed

• Even the local infiltration did not produce any

perceptible sensory loss

• Patient observed for 2 hours in PACU and then

sent back to the ward

• Discharged on 10th Post operative day after

uneventful stay

Discussion• Spinal anesthesia is not a 100% certain successful

technique.

• Failure rates of 0.72% to 16.0% have been reported

• Causes of failed spinal anesthesia can be classified as

1. Technical Failure to enter the subarachnoid space: no drug

injection

2. Successfully injected drug may be maldistributed relative to

the need of the planned surgery

3. Un-recognized failed injection of the drug: partial or total

4. Drug errors : wrong drugs, inappropriate doses/ additives

Discussion

5. Pseudo block failure: excessive expectation for speed of block onset

6. Subdural injection of the spinal dose: possible cause, but never

reported

7. Central neuroplasticity in Phantom limb pain and Human model of

tachyphylaxis

8. Local Anaesthetic Resistance: Genetic or acquired;

these are mystifying circumstances, as in our case, when there is

failure of spinal block, despite apparent technically correct injection

of the correct dose of drug

Discussion• Mechanism of Local Anaesthetic Resistance: Receptor Mutation with Na+ Channel abnormalities Resulting from variation in the amino acid sequence

within the Na+ Channel

Na+ Channel consists of α, β1, β2 subunits

α subunit has 4 domains (I-IV), each made of

6 segments (S1-S6)• L.A. action is due to their interaction with S6-

IV D of α subunit (sites of Ph ala and Tyr A.A.residues)

• Variation/alteration at this site, can cause LAA resistance

Structure of a Na+ channel α‐subunit

Discussion• Scorpion Bites

• Common Phenomenon in Tropical/ subtropical Countries

• Scorpion venom neurotoxins possess general ability

to depolarise the excitable membranes due to an

increase in Na+ permeabilty of the resting membrane

and reduction in the rate and amount of Na

inactivation

• It may also modify Na pumping mechanism and

passive / active Na permeability systems

Discussion

• In acute phase : Pain, inflammation, N.M.

intoxication is due to venom acting on exposed

nerve or muscle fibers or N.M. Junction

• Muscular twitching/ fibrillations due to release of

neuro-transmitter/neurotoxins.

• Not much importance given to the past history of

scorpion bite by patients or anaesthesiologists

Discussion• We had similar type of presentation- failed spinal in some

patients in the past, but did not give significant importance to it

• Inability to block the peripheral nerves as well as failure of local

infiltration, high lights the possibility of resistance to local

anaesthetics as the most plausible explanation in this case

• Since the patient was bitten by scorpion twice and at multiple

sites, it could have caused development of antibodies

against the scorpion venom leading to competitive

antagonism at the receptor site ( S6-D IV of α subunit of

Na channel) where LAAs are supposed to act

Observation

With h/o scorpion bite • 2 cases of failed supraclavicular

brachial block, where local infiltration was also ineffective

• 3 cases of failed spinal• 7 cases of delayed effect of spinal

block• We are making it our practice to elicit

the history, routinely

Conclusion

• We are convinced about the hypothesis:

‘Scorpion Bites ( especially repeated

bites) may cause development of

resistance to the action of local

anaesthetics used to achieve blocks

by various routes!’

THAN

K

YOU!